Electric compressed gas circuit breaker

ABSTRACT

An electric compressed gas circuit breaker has cooperating stationary and movable contacts and an arc blasting assembly including a stationary blast piston and cooperating therewith, a blast cylinder made of electrically insulating material and having a bottom to which the movable contact is mounted. During circuit breaking, the cylinder&#39;&#39;s bottom is moved to separate the contacts, the cylinder having an end provided with a nozzle which, due to the cylinder&#39;&#39;s simultaneous movement relative to the stationary piston, further compresses the gas in which the assembly operates, so that an arc extinguishing blast is ejected through this nozzle. The cylinder is made from electrically insulating material and the bottom removably connects with the cylinder&#39;&#39;s end remote from its nozzle, by the cylinder&#39;&#39;s inside having a keyway and its bottom having a key cooperating with this keyway in a removable manner. Preferably a plurality of keyways and keys are provided which are circumferentially interspaced uniformly so that the mechanical stress resulting from the transmission of force between the bottom and the cylinder is distributed uniformly throughout the cylinder.

Primary Examiner-Robert S. Macon Attorney, Agent, or Firm-Hugh A. Chapin O United States Patent [191 [111 3,787,652

Konczal Jan. 22, 1974 1 ELECTRIC COMPRESSED GAS CIRCUlT [57] ABSTRACT BREAKER An electric compressed gas circuit breaker has coop- [75] Inventor: Wolfgang K l, B li Germany erating stationary and movable contacts and an arc blasting assembly including a stationary blast piston [73] Asslgnee' gwmens Akuengeseuschafl Mumch and cooperating therewith, a blast cylinder made of ermany electrically insulating material and having a bottom to [22] Filed; Aug, 17, 1972 which the movable contact is mounted. During circuit breaking, the cylinders bottom is moved to separate [21] p 281495 the contacts, the cylinder having an end provided with g a nozzle which, due to the cylinders simultaneous [30] F i A li i P i i D t movement relative to the stationary piston, further Aug 3] i 1971 Germany P 21 44 215 9 compresses the gas in which the assembly operates, so that an arc extinguishing blast is ejected through this 52 us. Cl. 200/148 A 200/150 0 The cylinder is made electrically insulat- 51 Int. Cl. iioih 33/88 ihg material and hohm remmahly commas with [58] Field of Search 200/148 A 150 G the cylinders end Yemme fmm hs by the ders inside having a keyway and its bottom having a l 56] References Cited key cooperating with this keyway in a removable manner. Preferably a plurality of keyways and keys are UNITED STATES PATENTS provided which are circumferentiallyinterspaced uni- 3,588,407 6/1971 Frink 200/148 A formly so that the mechanical Stress resulting from the transmission of force between the bottom and the cylinder is distributed uniformly throughout the cylinder.

v 6 Claims, 4 Drawing Figures Pmwtumzmm SHEET 1 [IF 3 PATENTEDMZZ 1914 3781.652

SHEE'I 2 OF 3 Big. 2

ELECTRIC COMPRESSED GAS CIRCUIT BREAKER BACKGROUND OF THE INVENTION An electric compressed gas circuit breaker has its elements operating in an electrically insulating housing confining compressed gas surrounding these elements. These elements include cooperating stationary and movable contacts, the movable contact being operated by a mechanism responsive to electrical overloading or other conditions to quickly move the movable contact from the stationary contact to break the electric circuit protected or controlled by the circuit breaker. When the electrical potential and power involved is enough to result in an arc being drawn between the separating contacts, an arc blasting assembly may be used, which further compresses the compressed gas and ejects the gas through a nozzle directed to blast out the arc.

DESCRIPTION OF THE PRIOR ART German Pat. No. 1,069,740 discloses the concept of such a circuit breaker having a blast cylinder connected to move with the movable contact so that the two are moved together during the circuit breaking action, the blast cylinder containing a stationary piston and further compressing the compressed gas by the relative movement between it and the cylinder, and the latter having a gas jet nozzle which ejects this further compressed gas into the are.

In the above patented construction the blast cylinder is reciprocatively mounted and guided by a plurality of cooperating guide rods interassociated by rollers, and

the cylinder has external laterally projecting arms for with the movable contact mechanically connected with this cylinders bottom, and with the latter connecting with this cylinder in a movable manner to permit simplified initial assembly of the parts and subsequent easy servicing, and in such a manner that the mechanical stresses involved during circuit breaking and blast creating are distributed circumferentially uniformly and widely throughout the cylinders wall as is desirable when the latter is made from insulating material.

According to the invention, this object is attained by making the blast cylinders bottom separate from the blast cylinder and inserted in the lower end of the latter, the bottom s periphery axially slidably engaging the cylinders inner surface, the latter being formed with a radially extending keyway means and the bottom having key means extending therefrom radially into this keyway means, the key means having means for releasably fastening them to this bottom to fasten the latter and the cylinder together.

The keyway means may comprise one or more lateral openings from the cylinders inner surface and extending partially or completely through the cylinders wall. To effect a uniform distribution of the mechanical stresses, this keyway means may comprise a plurality of openingsas described, and which are uniformly interspaced circumferentially around the cylinder, the key means comprising a corresponding number of keys with each provided with the fastening means. By making the keyway openings circumferentially elongated, and the keys in the form of flat keys extending through these openings. the mechanical stress is widely distributed throughout the cylinder wall. Preferably, the ef- In the above referred to circuit breaker, the end of the blast cylinder, which moves towards the piston and which may be referred to as the top end, mounts both the movable electric contact and the blast nozzle; and the cylinder, through its external laterally projecting arms, receives the actuating force during circuit breaking. Therefore, the cylinder is subject to high stresses and is made of metal.

In another form, shown by German published patent application No. 1,913,969, the blast cylinder does not require the space-occupying external laterally projecting arms because the movable contact is connected with the blast cylinder's bottom, by which is meant the blast cylinders end opposite its end having the gas blast nozzle. Therefore, the blast cylinder can be pulled or actuated, to open the circuit and create the blast, by means other than the external laterally projecting arms or the like.

SUMMARY OF THE INVENTION One object of the present invention is to provide an electric compressed gas circuit breaker with an arc blasting assembly of the type described, with the blast cylinder made of electrically insulating material and fective contact area between the flat keys and the cylinder wall openings should collectively provide an effec tive contact area of at least 20 percent of the crosssectional area of the cylinders wall. By providing at least three of the keyway openings, the cylinder wall is held rigidly with respect to the cylinders bottom so that it is reciprocatively guided and supported thereby in its proper reciprocative travel path. The movable contact can be connected to the cylinders bottom.

It follows that with this are blasting assembly, the cylinder may be made of insulating material which, of course, is of less mechanical strength than metal; the need for external radially projecting arms is eliminated, thereby permitting a smaller overall circuit breaker housing, and initial assembly and subsequent servicing is simplified.

DESCRIPTION OF THE DRAWINGS Having reference to the accompanying drawings:

FIG. 1, in longitudinal section, schematicallyshows a high voltage power circuit breaker with a blasting assembly, the parts being shown on the right-hand side of the broken line in the circuit closing position and on the left-hand side of this line being shown in circuit breaking position;

FIG. 2, in longitudinal section, shows the blast cylinder bottom construction of the present invention;

FIG. 3 shows a bottom end view of FIG. 2 and FIG. 4 is an elevation of a segment of FIG. 3, as indicated on the line 4-4 in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. I, it is to be understood that this isdrawn in an extremely schematic and simplified manner for the purpose of showing the general con-- struction and operation of a compressed gas circuit breaker adapted for use with high voltage electric power currents.

In this figure only a portion of the fully enclosing housing 1 of the circuit breaker is shown. This housing may be cylindrical and made of insulating material and confines the compressed gas. The gas may be SF A stationary electric contact 2 is positioned in the upper end of the housing 1 and supported by the latter by means which are not shown. The movable contact 3 is connected with the blast cylinder 4 made of insulating material, this contact 3 and cylinder 4 being actuated together by an actuator or drive rod 5 connected with a suitable mechanism (not shown) which, when tripped for any reason, pulls the rod 5 downwardly, this rod connecting with the blast cylinders bottom 6 to which both the contact 3 and cylinder 4 are connected. A stationary annular piston 7 is positioned inside of the cylinder 4 by a plurality of supporting members 8 which pass through holes 6a in the cylinders bottom 6. The upper end of the blast cylinder 4 is closed excepting for the blast jet orifice 9.

When the contact 3 and cylinder 4 are in the circuitopen position, as represented on the left side of the broken line in FIG. 1, and are then moved to the circuitclosed position shown on the right side of this line, the blast cylinder 4 becomes filled with the compressed gas 1 in the housing 1. When the circuit breaker mechanism is tripped by an electrical overload or for other reasons, the tubular drive rod 5 is pulled downwardly very rapidly, the stationary piston 7 on which the blast cylinder slides ejecting the compressed gas in the form of a blast through the blast orifice 9, and blasting out any arc that may form.

It can be seen that the actuating force exerted by the drive rod 5 is applied to the blast cylinders bottom 6 which mounts both the movable contact 3 and the cylinder 4, and that enough force must be involved to mechanically separate the contacts and to further compress the compressed gas to produce the arc extinguishing blast. This force must be transmitted to the lower end of the blast cylinder 4 through its bottom 6.

In FIGS. 2 and 3 only the parts required to illustrate the principles of the present invention are shown. Thus, the holes 6a of FIG. 1 are not shown and the movable contact 3 is also eliminated. The present invention is concerned with the connection of the cylinder 4 with its bottom 6.

As shown by FIG. 2, the bottom 6 is separate from the cylinder 4, the latter being made, for example, of alaminated molded plastic. The bottoms periphery 6a axially slidably engages the inner surface of the cylinder 4 adjacent to the lower end of the cylinder. The cylinder's inner surface is formed with a radially extending for each key.

In more detail, the keyway means or openings 11 comprise a plurality of circumferentially elongated openings extending through the cylinders wall and the key means or keys are in the form of flat keys extending through these openings. These flat keys each have a width substantially equaling that of the keyway openings l0, and preferably the latter are provided with round ends 13 to avoid sharp corners which might introduce stress concentrations in the wall of the cylinder 4 which is made of insulating materiaL' It is to be understood that the drive rod 5, the bottom 6, the keys 11 and the fastenings 12, may all be made of metal and are, therefore, easily designed to have adequate structural strength to handle the load imposed by the rapid movement involved by the circuit breaker operation. Because the wall of the cylinder 4 is made of electrically insulating material, and therefore non-' metallic material, and because this wall should not be made unnecessarily thick to perform its blast forming function, its ability to handle the mechanical force involved requires attention. With this in mind, the keyway openings 10 and the flat keys 11 are designed to provide cooperative interengaging surfaces providing collectively or together an effective contact area of at least 20 percent of the cross-sectional area of the cylinders wall. This minimum should be kept in mind in the event the keyway openings are not formed completely through the wall of the cylinder 4 but are in the form of blind or bottomed recesses, this construction not being shown but being a possibility.

The fastening means 12 are accessible from the outside or the bottom side of the cylinders bottom 6. In detail, the fastenings 12 are in the form of cap screws which are passed through holes 11a formed in the keys and screwed into threaded holes 6c formed in the bottom 6. The heads 12a of the cap screws are on the outside or bottom side of the keys ll. Therefore, these fastenings are accessible from the outside or bottom side of the cylinders bottom 6.

It should be kept in mind that in FIGS. 2 and 3 the stationary piston 7, its supporting members 8, the openings through the bottom 6 required for passage of these members 8, and the movable contact 3, are not shown. However, it should be remembered that the drive force of the drive rod 5 must be transmitted to the movable contact 3, the cylinder 4 which slides on the piston 7, and all of the parts required to define the blast jet orifice 9; and that the force of this drive rod is applied suddenly during circuit breaking operation and must be adequate to' overcome the inertia of the parts, any contact separating force that might be required, and to compress the gas to produce the arc extinguishing blast.

Although a minimum number of three has been suggested for the keyway means and the key means, this is because at least this number is required to assure that the blast cylinder 4 receives the force in a distributed manner and is properly guided in its reciprocative path,

without requiring any need for the cylinder having ex-' ternal supports or external drive connection means.

Actually in FIG. 2, six of these releasable fastening means are illustrated and even moremight be used design requirements indicate, when considering the strength of the cylinder wall' made of insulating material.

With this new construction an electric compressedgas circuit breaker may be made more compactly, particularly in its transverse or lateral direction. During assembly, the installation of the blast cylinder with its associated drive, such as the drive rod 5 and the necessary bottom 6 to which the movable contact is connected, is easily effected. Disassembly for servicing is obviously easy. Although not specifically described before, it is to be understood that, for assembly, the drive 5 and bottom 6, and the movable contact when carried by the bottom 6, may be inserted in the cylinder 4, the various keys 11 easily positioned, and the cap screws 12 screwed into place to complete a rigid assembly both supporting the cylinder and transmitting to it the necessarily quickly applied force during circuit breaking operation. Because the heads of the cap screws 12 are external, these fastenings may be easily unscrewed, the keys removed, and the construction disassembled for servicing when necessary.

I claim:

1. An electric compressed gas circuit breaker having cooperating stationary and movable contacts and an arc blasting assembly including a stationary blast piston and cooperating therewith a blast cylinder made of electrically insulating material and having a bottom to which said movable contact is mounted; wherein the improvement comprises said bottom being separate from said cylinder and inserted therein with the bottoms periphery axially slideably engaging the cylinders inner surface, the latter being formed with a radially extending keyway means and said bottom having key means extending therefrom radially into said keyway means, and means for removably fastening said key means to said bottom to fasten the latter and said cylinder together disposed axially with respect to said cylinder and accessible from the bottom side of said bottom.

2. The circuit breaker of claim 1 in which said keyway means is an opening extending completely through the wall of said cylinder. l

3. The circuit breaker of claim 1 in which said keyway means comprises a plurality of openings extending radially through said cylinder and uniformly interspaced circumferentially around said cylinder and said key means comprises a corresponding number of keys with said fastening means provided for each key.

4. The circuit breaker of claim 1 in which said keyway means comprises a plurality of circumferentially elongated openings extending through said cylinders wall and said key means comprises a corresponding number of flat keys extending through said openings with said fastening means provided individually for each key.

5. The circuit breaker of claim 4 in which said openings and flat keys form cooperative interengaging surfaces providing all together an effective contact area of at least 20 percent of the cross-sectional area of said cylinders wall.

6. The circuit breaker of claim 4 in which there are at least three of said openings and all of said openings are uniformly interspaced circumferentially around said wall, a corresponding number of said keys and their said fastening means being provided, said fastening means being accessible from the outside of said bottom. 

1. An electric compressed gas circuit breaker having cooperating stationary and movable contacts and an arC blasting assembly including a stationary blast piston and cooperating therewith a blast cylinder made of electrically insulating material and having a bottom to which said movable contact is mounted; wherein the improvement comprises said bottom being separate from said cylinder and inserted therein with the bottom''s periphery axially slideably engaging the cylinder''s inner surface, the latter being formed with a radially extending keyway means and said bottom having key means extending therefrom radially into said keyway means, and means for removably fastening said key means to said bottom to fasten the latter and said cylinder together disposed axially with respect to said cylinder and accessible from the bottom side of said bottom.
 2. The circuit breaker of claim 1 in which said keyway means is an opening extending completely through the wall of said cylinder.
 3. The circuit breaker of claim 1 in which said keyway means comprises a plurality of openings extending radially through said cylinder and uniformly interspaced circumferentially around said cylinder and said key means comprises a corresponding number of keys with said fastening means provided for each key.
 4. The circuit breaker of claim 1 in which said keyway means comprises a plurality of circumferentially elongated openings extending through said cylinder''s wall and said key means comprises a corresponding number of flat keys extending through said openings with said fastening means provided individually for each key.
 5. The circuit breaker of claim 4 in which said openings and flat keys form cooperative interengaging surfaces providing all together an effective contact area of at least 20 percent of the cross-sectional area of said cylinder''s wall.
 6. The circuit breaker of claim 4 in which there are at least three of said openings and all of said openings are uniformly interspaced circumferentially around said wall, a corresponding number of said keys and their said fastening means being provided, said fastening means being accessible from the outside of said bottom. 